Juice Press dismissed the notion that the company's fructose-sweetened drinks cause a crash.

"Some people don't do well when they have a lot of fruit sugar. Some people do great — they have tons of energy," says Alex Jay, associate director of marketing and a certified health coach.

Advertisement

And, she adds, "fruit sugar actually serves a purpose and it has vitamins in it. White sugar, you're not getting any vitamins."

BluePrint Cleanse (Handout)

Fat is also a problem with some cleanses. A day on Organic Avenue's Love Easy cleanse - which includes some food - will stuff 107 grams of fat into your body.

The total calories of the cleanse — 1,880 — are about right for the day, but fat makes up close to half the calories in this cleanse. Juice Press' cleanse is a little better, with 340 fat grams, but still over the 25%-30% of your daily intake that should come from fat.

"It is impossible to get balance in a cleanse," says Batayneh.

Jocelyn Levy, a 28-year-old branding consultant, did several juice cleanses, including BluePrint, but they made her feel sluggish and unwell.

"I was looking for a quick fix, but I was extremely lethargic and getting stomach pains and mood swings," she says. Now, "I'm very anti-juice cleanse."

No major juice company would comment at length on the issue, but here's what the experts say to counter the juice cleanse's rainbow-colored claims:

1. Your body is self-cleaning

"The kidney, colon and liver are efficient in cleansing and eliminating toxins," says Vicario. "Our body is built to cleanse itself constantly," adds Dr. Zelana Montminy , who is certified in nutrition, and is the health and wellness expert at the entertainment website PopSugar. "We're always undergoing chemical reactions within our bodies to detoxify."

Dietician Heather Bauer says cleanses are not a good way to lose weight. (Handout)

2. No weigh!

Cleanse companies claim their juices are for health, not weight loss, but they're cheeky about it, too. "If you do lose weight, (then) that's just a happy side effect," Blueprint's website says. Prepare to be unhappy. A five-day reprieve from solid food will likely take off some weight, but it almost always will be temporary. "It's not a reasonable approach to lose weight," says Heather Bauer, a registered dietician, nutritionist and founder of Bestowed, a healthy-food subscription box. "It's water weight. It's not real poundage."

To provide balance for this story, we reached out to the major juice cleanse companies, but none would comment at length. As such, we offer this passage from the Juice Press cleanse site (altered only to capitalize the first letter of sentences):

"When you give your body a total rest, including from digesting foods, we believe that your body in its infinite wisdom diverts vital healing forces into areas of the body that need attention.

"Overeating is also toxic. It results in fermentation and intercellular gases. It causes food to digest poorly and rot in the digestive system, which allows toxic bacteria to proliferate, and of course, causes more fermentation and creates more gases. A dirty upper gastrointestinal tract is at the root of many degenerative and acute illnesses. This is science.

"Other common dietary mistakes such as eating processed foods, bad food combinations, eating late at night, consuming too much protein, to name a few, are also the source of health problems. These statements are irrefutable science.

"The benefit of a juice fast is that you are leaving out all of these mistakes. For every mistake you leave out, there is an immediate reciprocal improvement in your overall chemistry. The reason is linked to what is called vital force — something many health care professionals sadly know nothing about. Vital force enables an immunological response by your body to cleanse and self-heal."